1. Field of the Invention
The invention relates to an improved electromagnetically actuated valve arrangement of the type useful, for example, in brake systems for motor vehicles.
2. Description of the Prior Art
From German Patent Disclosure DE 100 36 576 A1, an electromagnetically actuatable valve arrangement which is usable particularly in hydraulic brake systems of motor vehicles is known. The valve arrangement includes a valve insert embodied with a longitudinal bore and solidly connected to a valve dome. Disposed in the valve dome is an armature, longitudinally movable in the axial direction of the valve arrangement, that is operatively connected to a valve tappet guided longitudinally movably, likewise in the axial direction, in the valve insert. The operative connection between the armature and the valve tappet or the valve element is such that an armature motion in the closing direction of a valve seat is transmitted to the valve tappet embodied with a closing member, so that a seat valve is closed upon contact of the closing member with a valve seat.
The valve tappet is guided with slight radial play in the longitudinal bore of the valve insert and is provided on its jacket side with at least two conduits, separate from one another. A valve chamber containing the seat valve of the valve arrangement communicates fluidically through the conduits with voids inside the valve dome, so that residual air in the valve dome can be positively displaced via the conduits.
The valve arrangement, in the currentless state, is furthermore kept in the opened state by a spring assembly or a restoring spring; the spring assembly, embodied as a compression spring, is built into the valve chamber. This disposition of the spring assembly assures simple assembly of the valve arrangement.
By actuation of the valve arrangement which is open when without current, the armature is displaced with the valve element. Between the voids, which are defined on the end facing away from the valve element by the valve dome and the armature and in the contact region of the armature on the valve element by the armature, the valve element, the valve dome, and the valve insert, a volumetric and pressure compensation takes place, which in operation of the valve arrangement is associated with a flow of the operating fluid located in the interior of the valve arrangement.
The fluid flow, in unfavorable operating states of the valve arrangement, in the region of the end faces, facing toward one another, of the armature and of the valve insert, leads to an unwanted motion of the armature and thus also of the valve element in the direction of the valve seat, which is due to an effect of the hydrodynamic paradox that occurs between the end faces of the armature and of the valve insert.
This unwanted motion of the armature and of the valve element in the direction of the valve seat leads, in operation of the valve arrangement, to an uncontrollable change in location of the armature and also of the valve element, which under some circumstances leads to an unwanted change in the flow cross section of the valve arrangement in the region of the valve seat, and as a result an open-and closed-loop control characteristic of the valve arrangement can be verified or replicated only with difficulty.